Problem List

1. CPP Setup
2. Cpp Basics
3. Java Setup
4. Java Basics
5. Java OOPs Basic
6. Input Output Easy
7. If Else Adult Teen Problem Easy
8. If ElseIf Easy
9. Switch Case Easy
10. Sum of first last element in array Easy
11. Print X N numbers of times Easy
12. Print last character of string Easy
13. Easy and Medium
14. Hard
15. Pattern 1 Easy
16. Pattern 2 Easy
17. Pattern 3 Easy
18. Pattern 4 Easy
19. Pattern 5 Easy
20. Pattern 6 Easy
21. Pattern 7 Easy
22. Pattern 8 Easy
23. Pattern 9 Easy
24. Pattern 10 Easy
25. Pattern 11 Easy
26. Pattern 12 Easy
27. Pattern 13 Easy
28. Pattern 14 Easy
29. Pattern 15 Easy
30. Pattern 16 Easy
31. Pattern 17 Easy
32. Pattern 18 Easy
33. Pattern 19 Easy
34. Pattern 20 Medium
35. Pattern 21 Medium
36. Pattern 22 Medium
37. Theory with examples
38. STL
39. Java Collections
40. Basic Maths
41. Basic Arrays
42. Basic Hashing
43. Basic String
44. Count all digits of a number Easy
45. Count number of odd digits in a number Easy
46. Reverse a number Easy
47. Palindrome number Easy
48. Return the largest digit in a number Easy
49. Factorial of a given number Easy
50. Check if the number is armstrong Easy
51. Check for perfect number Easy
52. Check for prime number Easy
53. Count of prime numbers till N Easy
54. GCD of two numbers Easy
55. LCM of two numbers Easy
56. Divisors of a number Easy
57. Sum of array elements Easy
58. Count of odd numbers in array Easy
59. Reverse an array Easy
60. Check if the array is sorted Easy
61. Highest occurring element in an array Easy
62. Second highest occurring element Easy
63. Sum of highest and lowest frequency Easy
64. Reverse a string Easy
65. Palindrome Check Easy
66. Largest odd number in a string Easy
67. Longest common prefix Easy
68. Isomorphic string Easy
69. Rotate string Easy
70. Valid Anagram Easy
71. Sort characters by frequency Easy
72. Recursion Theory
73. Recursion Concepts with Parameters
74. Sum of first N numbers Easy
75. Factorial of a given number Easy
76. Sum of array elements Easy
77. Reverse a string Easy
78. Check if string is palindrome or not Easy
79. Check if a number is prime or not Easy
80. Reverse an array Easy
81. Check if the array is sorted Easy
82. Sum of digits in a given number Easy
83. Fibonacci Number Easy
84. Selection Sort Easy
85. Bubble Sort Easy
86. Insertion Sorting Easy
87. Merge Sorting Medium
88. Quick Sorting Easy
89. Linear Search Easy
90. Largest Element Easy
91. Second Largest Element Easy
92. Maximum Consecutive Ones Easy
93. Left Rotate Array by One Easy
94. Left Rotate Array by K Places Easy
95. Move Zeros to End Easy
96. Remove duplicates from sorted array Easy
97. Find missing number Easy
98. Union of two sorted arrays Easy
99. Intersection of two sorted arrays Easy
100. Leaders in an Array Medium
101. Print the matrix in spiral manner Medium
102. Rearrange array elements by sign Medium
103. Pascal's Triangle Medium
104. Rotate matrix by 90 degrees Medium
105. Two Sum Medium
106. 3 Sum Medium
107. 4 Sum Medium
108. Sort an array of 0's 1's and 2's Medium
109. Kadane's Algorithm Medium
110. Majority Element-I Hard
111. Majority Element-II Hard
112. Find the repeating and missing number Hard
113. Count Inversions Hard
114. Reverse Pairs Hard
115. Maximum Product Subarray in an Array Hard
116. Merge two sorted arrays without extra space Hard
117. Maximum Consecutive Good Numbers Easy
118. Set difference of two arrays Easy
119. Number of Jumps Easy
120. Longest Consecutive Sequence in an Array Hard
121. Longest subarray with sum K Hard
122. Count subarrays with given sum Hard
123. Count subarrays with given xor K Hard
124. Count of Subarrays with Sum Divisible by K Easy
125. Group Words by Anagrams Easy
126. Maximum Points on a Line Easy
127. Search X in sorted array Easy
128. Lower Bound Easy
129. Upper Bound Easy
130. Search insert position Easy
131. Floor and Ceil in Sorted Array Easy
132. First and last occurrence Easy
133. Search in rotated sorted array-I Easy
134. Search in rotated sorted array-II Easy
135. Find minimum in Rotated Sorted Array Easy
136. Find out how many times the array is rotated Easy
137. Single element in sorted array Medium
138. Find square root of a number Medium
139. Find Nth root of a number Medium
140. Find the smallest divisor Medium
141. Koko eating bananas Medium
142. Minimum days to make M bouquets Medium
143. Aggressive Cows Hard
144. Book Allocation Problem Hard
145. Find peak element Hard
146. Median of 2 sorted arrays Hard
147. Minimise max distance to gas stations Hard
148. Kth element of 2 sorted arrays Hard
149. Split array - largest sum Hard
150. Find row with maximum 1's Hard
151. Search in a 2D matrix Hard
152. Search in 2D matrix - II Hard
153. Find Peak Element Hard
154. Matrix Median Hard
155. Cleaning Windows Easy
156. Neighbours within k distance Easy
157. Z-Score Easy
158. Pow(x,n) Easy
159. Generate Paranthesis Easy
160. Power Set Easy
161. Check if there exists a subsequence with sum K Easy
162. Count all subsequences with sum K Easy
163. Combination Sum Medium
164. Combination Sum II Medium
165. Subsets I Medium
166. Subsets II Medium
167. Combination Sum III Medium
168. Letter Combinations of a Phone Number Hard
169. Palindrome partitioning Hard
170. Word Search Hard
171. N Queen Hard
172. Rat in a Maze Hard
173. M Coloring Problem Hard
174. Sudoko Solver Hard
175. Different Series Easy
176. Combination XOR Easy
177. Find Distinct Expressions Easy
178. Introduction to Singly LinkedList
179. Traversal in Linked List Easy
180. Deletion in Linked List
181. Insertion in Linked List
182. Deletion of the head of LL Easy
183. Deletion of the tail of LL Easy
184. Deletion of the Kth element of LL Easy
185. Delete the element with value X Easy
186. Insertion at the head of LL Easy
187. Insertion at the tail of LL Easy
188. Insertion at the Kth position of LL Easy
189. Insertion before the value X in LL Easy
190. Introduction to Doubly LL
191. Deletion in Doubly LL
192. Insertion in DLL
193. Convert Array to DLL Easy
194. Delete head of DLL Easy
195. Delete Tail of DLL Easy
196. Delete Kth Element of DLL Easy
197. Removing given node in DLL Easy
198. Insert node before head in DLL Easy
199. Insert node before tail in DLL Easy
200. Insert node before (kth node) in DLL Easy
201. Insert before given node in DLL Easy
202. Add two numbers in LL Medium
203. Segregate odd and even nodes in LL Medium
204. Sort a LL of 0's 1's and 2's Medium
205. Remove Nth node from the back of the LL Medium
206. Reverse a LL Medium
207. Add one to a number represented by LL Medium
208. Check if LL is palindrome or not Medium
209. Find the intersection point of Y LL Medium
210. Detect a loop in LL Medium
211. Find the starting point in LL Medium
212. Length of loop in LL Medium
213. Delete the middle node in LL Medium
214. Reverse LL in group of given size K Hard
215. Rotate a LL Hard
216. Merge two Sorted Lists Hard
217. Flattening of LL Hard
218. Sort LL Hard
219. Clone a LL with random and next pointer Hard
220. Delete all occurrences of a key in DLL Hard
221. Remove duplicated from sorted DLL Hard
222. Remove bad elements in Linked List Easy
223. Segregate Nodes into 3 parts in LL Easy
224. Special Linked List Easy
225. Introduction to Bits and Tricks
226. Minimum Bit Flips to Convert Number Medium
227. Single Number - I Medium
228. Single Number - II Medium
229. Single Number - III Medium
230. Divide two numbers without multiplication and division Medium
231. Power Set Bit Manipulation Medium
232. XOR of numbers in a given range Medium
233. Count Set Cost Easy
234. Twin Numbers Easy
235. Odd Subsets Easy
236. Assign Cookies Easy
237. Lemonade Change Easy
238. Jump Game - I Easy
239. Shortest Job First Medium
240. Job sequencing Problem Medium
241. N meetings in one room Medium
242. Non-overlapping Intervals Medium
243. Insert Interval Medium
244. Minimum number of platforms required for a railway Medium
245. Valid Paranthesis Checker Hard
246. Candy Hard
247. Maximum XOR Length Easy
248. Un Palindromic Strings Easy
249. Maximum sum Easy
250. Theory
251. Maximum Points You Can Obtain from Cards Medium
252. Longest Substring Without Repeating Characters Hard
253. Max Consecutive Ones III Hard
254. Fruit Into Baskets Hard
255. Longest Substring With At Most K Distinct Characters Hard
256. Longest Repeating Character Replacement Hard
257. Minimum Window Substring Hard
258. Number of Substrings Containing All Three Characters Hard
259. Binary Subarrays With Sum Hard
260. Count number of Nice subarrays Hard
261. Max Odd Numbers in K Window Medium
262. Maximum Good Subarray Length Medium
263. Number of Subarrays with Or less than K Hard
264. Implementation using different DS
265. Implement Stack using Arrays Easy
266. Implement Queue using Arrays Easy
267. Implement Stack using Queue Easy
268. Implement Queue using Stack Easy
269. Implement stack using Linkedlist Easy
270. Implement queue using Linkedlist Easy
271. Balanced Paranthesis Easy
272. Next Greater Element Medium
273. Next Greater Element - 2 Medium
274. Asteroid Collision Medium
275. Sum of Subarray Minimums Medium
276. Sum of Subarray Ranges Medium
277. Remove K Digits Medium
278. Implement Min Stack Hard
279. Sliding Window Maximum Hard
280. Trapping Rainwater Hard
281. Largest rectangle in a histogram Hard
282. Maximum Rectangles Hard
283. Stock span problem Hard
284. Celebrity Problem Hard
285. LRU Cache Hard
286. LFU Cache Hard
287. Count Collisons Easy
288. Lexicographically Smallest String Easy
289. Maximum Value Of A Subarray Easy
290. Introduction
291. Preorder Traversal Easy
292. Inorder Traversal Easy
293. Postorder Traversal Easy
294. Level Order Traversal Easy
295. Pre, Post, Inorder in one traversal Easy
296. Maximum Depth in BT Medium
297. Check if two trees are identical or not Medium
298. Check for balanced binary tree Medium
299. Diameter of Binary Tree Medium
300. Maximum path sum Medium
301. Check for symmetrical BTs Medium
302. Zig Zag or Spiral Traversal Medium
303. Boundary Traversal Medium
304. Vertical Order Traversal Medium
305. Top View of BT Medium
306. Bottom view of BT Medium
307. Right/Left View of BT Medium
308. Print root to node path in BT Hard
309. LCA in BT Hard
310. Maximum Width of BT Medium
311. Print all nodes at a distance of K in BT Hard
312. Minimum time taken to burn the BT from a given Node Hard
313. Count total nodes in a complete BT Hard
314. Requirements needed to construct a unique BT Hard
315. Construct a BT from Preorder and Inorder Hard
316. Construct a BT from Postorder and Inorder Hard
317. Serialize and De-serialize BT Hard
318. Morris Inorder Traversal Hard
319. Morris Preorder Traversal Hard
320. Minimum Travel Cost Easy
321. Maximum subtree sum Easy
322. Tree Greatness Easy
323. Introduction to BST
324. Search in BST Easy
325. Floor and Ceil in a BST Easy
326. Insert a given node in BST Medium
327. Delete a node in BST Medium
328. Kth Smallest and Largest element in BST Medium
329. Check if a tree is a BST or not Medium
330. LCA in BST Medium
331. Construct a BST from a preorder traversal Medium
332. Inorder successor and predecessor in BST Medium
333. BST iterator Hard
334. Two sum in BST Hard
335. Correct BST with two nodes swapped Hard
336. Largest BST in Binary Tree Hard
337. Range Sum in BST Easy
338. Great Tree Medium
339. Heaps (Theory Video)
340. Heapify Algorithm Medium
341. Build heap from a given Array Medium
342. Implement Min Heap Medium
343. Implement Max Heap Medium
344. Check if an array represents a min heap Medium
345. Convert Min Heap to Max Heap Medium
346. Heap Sort Medium
347. K-th Largest element in an array Medium
348. Kth largest element in a stream of running integers Hard
349. K Nearest Integers Easy
350. Minimum Operations To Exceed Target Easy
351. Furthest Reachable Mountain Easy
352. Introduction to Graph
353. Connected Components Medium
354. Traversal Techniques Medium
355. Number of provinces Medium
356. Number of islands Medium
357. Flood fill algorithm Medium
358. Number of enclaves Medium
359. Rotten Oranges Medium
360. Distance of nearest cell having one Medium
361. Surrounded Regions Medium
362. Number of distinct islands Medium
363. Detect a cycle in an undirected graph Hard
364. Bipartite graph Hard
365. Topological sort or Kahn's algorithm Hard
366. Detect a cycle in a directed graph Hard
367. Find eventual safe states Hard
368. Course Schedule I Hard
369. Course Schedule II Hard
370. Alien Dictionary Hard
371. Shortest path in DAG Hard
372. Shortest path in undirected graph with unit weights Hard
373. Word ladder I Hard
374. Word ladder II Hard
375. Dijkstra's algorithm Hard
376. Print Shortest Path Hard
377. Shortest Distance in a Binary Maze Hard
378. Path with minimum effort Hard
379. Cheapest flight within K stops Hard
380. Minimum multiplications to reach end Hard
381. Number of ways to arrive at destination Hard
382. Bellman ford algorithm Hard
383. Floyd warshall algorithm Hard
384. Find the city with the smallest number of neighbors Hard
385. MST theory
386. Disjoint Set Hard
387. Find the MST weight Hard
388. Number of operations to make network connected Hard
389. Accounts merge Hard
390. Number of islands II Hard
391. Making a large island Hard
392. Most stones removed with same row or column Hard
393. Kosaraju's algorithm Hard
394. Bridges in graph Hard
395. Articulation point in graph Hard
396. Furthest Empty Plot From Buildings Easy
397. Find All Possible Tasks Easy
398. Reachable Nodes Before Destruction Easy
399. Introduction to DP
400. Climbing stairs Medium
401. Frog Jump Medium
402. Frog jump with K distances Medium
403. Maximum sum of non adjacent elements Medium
404. House robber Medium
405. Ninja's training Medium
406. Grid unique paths Medium
407. Unique paths II Medium
408. Minimum path sum in grid Medium
409. Triangle Medium
410. Cherry pickup II Medium
411. Best time to buy and sell stock Medium
412. Best time to buy and sell stock II Medium
413. Best time to buy and sell stock III Medium
414. Best time to buy and sell stock IV Medium
415. Best time to buy and sell stock with transaction fees Medium
416. Subset sum equals to target Hard
417. Partition equal subset sum Hard
418. Partition a set into two subsets with minimum absolute sum difference Hard
419. Count subsets with sum K Hard
420. Count partitions with given difference Hard
421. 0 and 1 Knapsack Hard
422. Minimum coins Hard
423. Target sum Hard
424. Coin change II Hard
425. Unbounded knapsack Hard
426. Rod cutting problem Hard
427. Longest Increasing Subsequence Easy
428. Print Longest Increasing Subsequence Easy
429. Largest Divisible Subset Easy
430. Longest String Chain Easy
431. Longest Bitonic Subsequence Easy
432. Number of Longest Increasing Subsequences Easy
433. Longest common subsequence Hard
434. Longest common substring Hard
435. Longest palindromic subsequence Hard
436. Minimum insertions to make string palindrome Hard
437. Minimum insertions or deletions to convert string A to B Hard
438. Shortest common supersequence Hard
439. Distinct subsequences Hard
440. Edit distance Hard
441. Wildcard matching Hard
442. Matrix chain multiplication Hard
443. Minimum cost to cut the stick Hard
444. Burst balloons Hard
445. Palindrome partitioning II Hard
446. MEXX Easy
447. Buy Flowers Easy
448. Trie Implementation and Operations Hard
449. Trie Implementation and Advanced Operations Hard
450. Longest word with all prefixes Hard
451. Number of distinct substrings in a string Hard
452. Maximum XOR of two numbers in an array Hard
453. Maximum Xor with an element from an array Hard
454. Reverse every word in a string Hard
455. Minimum number of bracket reversals to make an expression balanced Hard
456. Count and say Hard
457. Rabin Karp Algorithm Hard
458. Z function Hard
459. KMP Algorithm or LPS array Hard
460. Shortest Palindrome Hard
461. Longest happy prefix Hard
462. Count Prefix Appearances
463. Distinct Substrings
464. Minimum Repetations
465. Print all primes till N Hard
466. Prime factorisation of a Number Hard
467. Count primes in range L to R Hard
468. Win or Lose Easy
469. Longest Factor Chain Easy

Java Basics

Beginner Problems Language Basics

Editorial

Watch the video for explanation, and to practice and read editorials around these problems, use the given below links.

Input Output
If Else Adult Teen Problem
If ElseIf
Switch Case
Sum of first last element in array
Print X N numbers of times
Print last character of string

Notes

Code

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